Health Experts Bust 7 Popular Fad Diets

You might be surprised.

Low carb, high fat, no fat, Paleo, intermittent fasting... The list goes on and on, with the arrival of each new fad diet confusing us further.

With many Australians overweight and obese, it's no surprise we look to diets that claim they are easy and will "make you lose weight fast". Unfortunately, these popular diets usually over-promise and under-deliver, leaving people feeling worse about themselves.

"Changing eating habits should occur gradually, especially if you have existing poor eating behaviours. A successful weight-loss program looks at many aspects including nutrition, exercise, hormone balance, stress management and proper sleep hygiene."

On top of this, when we're already unsure about proper nutrition, all these different diets spouting contrasting rules and restrictions are simply confusing us even more.

It's not a one size fits all. No one sticks a diet out long enough to see long-term, sustainable results.

"Changing eating habits also requires support and a complete lifestyle change, and the sad truth is that fad diets will not change the relationship people have with food," Clark said.

In saying this, there are certainly benefits to some diets -- namely, they often encourage people to ditch processed foods and eat more whole foods.

"For all of these diets, they result in cutting back on processed foods which is a great option for everyone, and cutting back calories as well, so if weight is not lost this is a surprise," accredited practising dietician Chloe McLeod told HuffPost Australia.

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Most fad diets are not only unsustainable but potentially dangerous.

According to Lauren McGuckin, an accredited practising dietitian and spokesperson for the Dietitians Association of Australia, diets may very well result in short-term weight loss, however are not sustainable for longer periods of time.

"The reason most of these diets work in the short term is because you are cutting out processed foods and focusing on whole foods, which is fantastic," McGuckin said.

"The problem we have with these fad diets comes from the fact that they cut out core foods groups and put other ones on a pedestal, which throws the diet out of whack.

"None of the diets are really promoting balance. It's not a 'one size fits all'. No one sticks a diet out long enough to see long-term, sustainable results."

Let's take a look at what these dietitians have to say about seven popular diets.

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1. Atkins

This diet approach promises that you can lose weight while you eat a diet rich in protein and fat and extremely low in carbs, and you shouldn't feel hungry or deprived.

Clark: "There are a lot of side effects associated with drastically cutting carbs, including headaches, dizziness, weakness, fatigue, constipation and irritability, as well as the potential to result in nutritional deficiencies.

"Some health professionals see this diet as potentially hazardous as low carbohydrate, high fat diets may increase cholesterol levels in the blood if the dietary fat is saturated or if dietary cholesterol is high. As a result, you may be at increased risk of heart disease.

"People can lose considerable amounts of weight quite quickly and early on in the diet, which can be very motivating. The diet also encourages people to cut out most processed carbs and alcohol."

It's an unbalanced diet and the risk lies in people following their own interpretation of the diet.

McLeod: "The Atkins diet encourages high intake of saturated fats and low carbs which often results in quick weight loss. However, most people regain the weight, plus extra."

McGuckin: "There is good evidence to suggest higher fat and lower carbohydrate diets are pretty effective in achieving weight loss in overweight and obese adults.

"However, it's only been studied in short periods of time and the conditions of these diets are studied is very controlled, meaning it's not representative of the general population following these diets. So we don't know whether the results are sustainable over a long period of time.

"It's an unbalanced diet and the risk lies in people following their own interpretation of the diet."

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Atkins and Dukan are not carb-friendly diets. *sighs*

2. Dukan

According to Clark, the Dukan diet is even more strict than the Atkins diet. However, unlike Atkins, it seriously restricts fat and replaces them with lean protein-rich foods.

Clark: "The pros of the Dukan diet is that weight loss can be expected and can help jumpstart a sluggish metabolism.

"However, similar to the Atkins diet, this diet is extremely restrictive and there is absolutely no room for flexibility as participants need to follow a prescribed set of rules. The dieting phases in this diet are very limited so there is a high chance participants will become bored very quickly and discontinue."

McLeod: "The Dukan diet is short-term fix and many people find it hard to stick to."

McGuckin: "The risk with any low carb diet is ketosis -- depending on how long people are on these diets for and how low carb they go, your brain becomes essentially starved of glucose.

"It really comes down to the quality of the carbohydrate you're choosing. We want people to eat moderate amounts of quality carbohydrates such as fresh fruit and vegetables and whole grains. This is a downside to the low carb diets as you're cutting back a whole food group and it can start to compromise your bowel function."

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We'll stay on the highway with all the avocados and nuts, thanks.

3. Intermittent fasting

Intermittent fasting diets such as 5:2 encourage people to restrict their calories on two fasting days in order to lose weight.

Clark: "Intermittent fasting certainly has its benefits to certain population groups. It has shown to reduce blood glucose, triglyceride and LDL cholesterol levels, which are all associated with a reduced risk of type 2 diabetes and cardiovascular disease. It may also reduce the risk of developing age-related conditions such as cancer and Alzheimer's disease.

"Although the diet states you can eat whatever you like on five days of the week, it doesn't provide participants a guide towards the variety of foods required for optimal nutrition.

"This diet can be potentially dangerous and should not be recommended for people who are pregnant or those taking certain medications."

Most of the time, people tend to eat whatever they like. It's not teaching healthy food habits, portion control or balance.

McLeod: "Intermittent fasting is one of the better diets out there as there is some research to back it. The main issue I have seen is many people struggle to stick with it or overdo it on the non-fast days."

McGuckin: "Being deprived of energy overall isn't great. You're going to lose concentration from lack of energy, so that side of it is quite unsafe.

"It does lower the overall energy intake but what you do on your days off is again open for interpretation. Most of the time, people tend to eat whatever they like. It's not teaching healthy food habits, portion control or balance.

"For people with eating disorders, this diet could potentially trigger that as you're depriving yourself of energy. It can also be risky for people with diabetes."

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These doughnuts are not safe on non-fasting days.

4. Paleo

Paleo's premise is that Paleolithic Era's eating habits are superior to those of the typical modern diet.

Clark: "Large amounts of vegetables, seeds and fruit along with avoidance of refined carbs, added salt and sugars is definitely considered to be healthy.

"The Paleo way of eating is a lifestyle and not a diet that is usually followed for a couple of weeks. It requires a lot of commitment and it comes at a cost as most food choices in the diet are expensive.

"The diet has a large emphasis on meat intake, which some health experts say should not be encouraged given associated increased heart disease risks. The diet also avoids two major food groups -- dairy and grains. Elimination of food groups may place you at risk of malnutrition and/or nutrient deficiencies if you do not balance your diet correctly."

McLeod: "I love how this diet encourages more whole foods, but I dislike that it encourages to cut out legumes, whole grains and dairy -- all of which have excellent health benefits."

McGuckin: "Paleo has got some good features like including more fruit and veggies. But, again it strips the diet of core foods groups such as your breads, cereals and dairy, and it's heavily reliant on protein."

5. Alkaline diet

The theory of this diet is that you need an optimal pH balance in your body to assist with weight loss, reduce inflammation and avoid certain diseases such as cancer.

Clark: "Although the positives of this diet is that it encourages a high consumption of fruit and vegetables and is based on real and unprocessed foods, there is no scientific evidence to show that this diet meets its claims.

"Our organs such as our kidneys and liver help to create our acid-base balance naturally, so our body does a good job or maintaining that balance without the need or assistance from a diet. Finally, we need an acidic environment in our gut to aid digestion and a disruption to this environment may contribute to gastrointestinal issues such as bloating, gas, diarrhoea and constipation."

McLeod: "There's not enough high quality research to back the theory behind this diet, though it generally recommends healthy options."

McGuckin: "There's not a lot of research backing up this diet. The Alkaline diet is quite healthy and focuses on increasing fruit and veggies and restricting processed junk foods which is always good, but in terms of reliable research and effectiveness, it's a bit far-fetched."

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Green smoothies are supposedly alkalising.

6. 1,200 calorie diets

The recommended average energy intake for an Australian adult is 2,000 calories, meaning this reduced calorie intake can result in weight loss -- at least to begin with.

Clark: "Consuming 1,200 calories per day is an easy way of ensuring a significant calorie deficit. However, determining a safe daily calorie deficit can be difficult because every person is different when it comes to baseline metabolism, body size and composition, sex, age, and level of physical activity.

"Depending on the aforementioned components which determine your individual calorie requirements, 1,200 calories may be too low for you. This can lead to physiological damage and nutrient deficiencies. Other challenges include hunger, dizziness, irritability and headaches due to a lack of nutrition.

"This diet requires strict monitoring and recording of food intake, which may lead to an obsession of calorie counting and a lack of focus on nutrient intake."

People often forget about nutrition and just think of food as calories and numbers, so their diets are generally unbalanced just so they fit into this calorie budget.

McLeod: "These low calorie diets work for some people in the short term, but it's only ever a short-term fix. Most people struggle to stick to it and regain weight."

McGuckin: "In terms of calorie counting, it's a really hard way of trying to lose weight. You're making hard work for life in general -- you have to weigh and measure everything. It does work, it's just not sustainable and very burdensome.

"People often forget about nutrition and just think of food as calories and numbers, so their diets are generally unbalanced just so they fit into this calorie budget."

7. No carbs after 5pm

This diet -- or diet rule -- dictates to stop eating carbohydrates after 5pm in order to lose weight.

Clark: "There is no solid scientific evidence to support the notion of avoiding carbs after 5pm for faster weight loss.

"It's important to note that if you eliminate starchy carbs such as pasta, rice, potato or bread at dinner, all you're eliminating is calories. There is nothing 'fat-burning' about the timing and you won't lose weight any faster by doing so."

McLeod: "This one is really just putting in food rules. It works well for some, but you can still lose weight and eat carbs after 5pm."

"When it comes to weight loss, overall calorie intake is important, but the most important thing is nutrition -- a good balance of food from every food group and not demonising one or over consuming another."